Can My Students Develop A Card Game Without Granting Me/the School Copyright?

hi everyone! (this is really low-stakes btw). i'm an instructor at an after school tutoring center. i wanted to know if my students can create and develop a card game and eventually distribute it without having to give up any copyright claims to me or the parent company. (this isn't a university, so i don't think there's any sort of "we own whatever you make" clause).

this is largely theoretical at this point—my students asked if they could sell their card game when they finished, and asked what i would do if it became a bestseller and made a lot of money. i told them it would be their intellectual property and they would own it 100% (well, 50%, since there are two of them).

i just want to make sure i can actually promise them this. i love how excited they are about this project and don't want to stifle their creativity by telling them they might have to give up some ownership to me or anyone else.